Backlit Beauty Dish

Abstract

The invention relates to a motor vehicle radar (2) protection device (1), comprising the following elements: a body (200) formed of a material transparent to radar waves (4) and light; a light source (300); a light reflector (400) formed of a material transparent to the radar waves (4); and a conductive heating track (12) arranged inside or on the surface of the body (200) made of transparent material. These elements are arranged so that a light beam (500) emitted by the light source (300) is reflected by the light reflector (400) toward the body (200) made of transparent material.

Description

Technical Field

[0001] The present invention relates to the field of motor vehicles equipped with radars and more particularly to the field of devices for shielding and protecting such radars, also called "radomes".

[0002] The device according to the invention is particularly applicable to radars arranged in the front or rear bumper of a vehicle, for example radars of the ACC type. Background Art

[0003] In particular for safety reasons, it is known to equip motor vehicles with radars, for example of the ACC (Adaptive Cruise Control) type. Such radars are used in particular to adjust the speed of the vehicle as a function of traffic and / or obstacles on the road. The radar detects the speed and distance of objects in front of the vehicle carrying it, in particular to maintain a safe distance between vehicles.

[0004] The ACC radar is mounted at the front or rear face of the vehicle, typically between the bars of the grille (which may be a cooling grille), but also on other body parts like fenders, for example for detecting cyclists.

[0005] In order to hide these radars for aesthetic reasons and / or to protect them from external intrusions (rain, ice, frost, mud, insects, leaves, etc.), it is known to use radomes, ie protective devices or parts comprising a plastic shield arranged in front of the radar.

[0006] Such plastic shielding allows radar waves to pass through with the lowest possible attenuation so as not to interfere with the operation of the radar itself.

[0007] From the application FR 3070547 of the same applicant, a decorated radome is known, which consists of a support opaque to light but transparent to radar waves, and a body transparent to radar waves and light, between which a diffusing light guide is arranged. This radome allows backlighting of a logo transparent to radar waves, present between the light guide and the transparent body, with the drawback that it requires the presence of a light guide in the emission cone of the radar (also called the detection field of the radar). This light guide can therefore interfere with the operation of the radar.

[0008] To remedy this drawback, the Applicant has proposed, in French application No. 19 04493, a radome equipped with light reflectors arranged to reflect the light beams emitted by the light sources of the radome towards the body of the radome, which is transparent to light and radar waves.

[0009] However, at temperatures below 10 degrees Celsius, the normal operation of the radome may be disrupted by the presence of ice, snow or frost, since the movement of the vehicle has a negative effect on the temperature. Therefore, the deposition of frost can be observed even at temperatures above zero. The frost layer interferes with the normal passage of electromagnetic waves and can cause errors in the measurement of external physical parameters.

[0010] To avoid frost deposits, which not only render auxiliary systems useless but may also generate false alarms, a defrost system is provided on the radome.

[0011] Such defrosting systems are traditionally formed by a heating track consisting of a wire capable of converting electrical energy into thermal energy by the Joule effect, the heating track being associated at each of its ends to two connecting plates to supply it with current, the whole being arranged on an element for a body part and being located near the sensor. The heat energy thus released allows the part to be defrosted locally in the event of a frost layer forming. In order to avoid interfering with the passage of electromagnetic waves, the heating track must be arranged according to a specific geometric configuration (hereinafter referred to as a "snake" arrangement). For the sake of clarity, a heating track arranged in a "snake" is defined as follows: the serpentine heating track follows a bull-ploughing (boustrophédon in French) route, i.e., it depicts parallel segments with a 180-degree turn between two segments, which are alternately oriented in one direction and then in another direction opposite to this direction, and the distance between the two parallel segments is constant.

[0012] By extension, a serpentine path refers to a path configured to allow electromagnetic waves within a certain frequency range of the radar to pass therethrough.

[0013] In fact, the accuracy of the arrangement of the heating track is very important to avoid it hindering the passage of electromagnetic waves, especially the parallelism between the different sections of the heating track and the spacing between these heating tracks must be ensured very accurately. Each electromagnetic wave frequency will correspond to an optimal configuration of the heating track arrangement so that the heating track is transparent to the passage of this electromagnetic wave. Summary of the invention

[0014] The invention aims in particular to provide a radome which is decorated with backlighting but allows optimal operation of the radar even in temperature conditions where layers of ice, snow or frost may form on the radome, in particular at temperatures below 10 degrees Celsius.

[0015] To this effect, the subject of the invention is a motor vehicle radar protection device comprising the following elements:

[0016] - a body formed of a material transparent to both radar waves and light;

[0017] -light source;

[0018] - a light reflector formed of a material transparent to radar waves; and

[0019] - an electrically conductive heating track arranged inside or at the surface of a body made of a transparent material,

[0020] These elements are arranged so that a light beam emitted by the light source is reflected by the light reflector toward the body made of a transparent material.

[0021] The absorptivity of a medium is a measure of its ability to absorb electromagnetic waves passing through it. The transmittance (or transmittance) of a medium is defined relative to the absorptivity. It is therefore the ratio of the flux that passes through the medium. For visible light, this is called transparency. Thus, a material is transparent to light when a portion of the visible light passes through it.

[0022] In the sense of the present invention, "transparent to radar waves" refers to a material that allows radar waves to pass through. The thickness of a material that is transparent to radar waves depends on the dielectric characteristics of the material (dielectric constant and loss factor) and the operating frequency of the radar.

[0023] Without being exhaustive, the material transparent to light and radar waves may be chosen from thermoplastic or thermosetting materials such as polycarbonate, polyamide, polypropylene, polymethyl methacrylate, copolyesters, acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, styrene acrylonitrile, a mixture of acrylonitrile styrene acrylate and polycarbonate, polycarbonate with polyethylene terephthalate, epoxy resins, polyurethanes.

[0024] This solution thus allows to provide a decorative radome with backlighting that has decorative advantages, since it prevents the formation of shadows in the logo image. Moreover, thanks to the backlighting system of the radome, the light source is not arranged in the emission cone of the radome, thus ensuring the proper functioning of the radome. Finally, the radome is compatible with the functioning of radars at temperatures below 10 degrees Celsius, and therefore even at temperatures that could cause the formation of ice, snow or frost layers on the radome.

[0025] Thus, the radome according to the invention can also be fitted to vehicles belonging to level 4 and level 5 according to the International Organization of Automobile Manufacturers (OICA) classification. These are respectively: for level 4, vehicles that can be driven without a driver under certain conditions; for level 5, vehicles that can be driven without a driver under all conditions. In fact, in these vehicles, the defrosting function of the radome is essential.

[0026] The radar protection device may employ the following other optional features alone or in combination:

[0027] The heating track comprises a connecting portion and a heating portion configured to allow passage of electromagnetic waves in the frequency range of the radar.

[0028] -The heating section is a serpentine section.

[0029] - an air cavity is provided between the light reflector and the transparent body. The air cavity allows thermal isolation of the heating element. As a result, for the same heating time, the high temperature can be maintained for a longer time. The effectiveness of defrosting is thereby increased. Furthermore, the air cavity is advantageous in that it enables better transmission of radar waves. Preferably, the thickness of the cavity is from half to twelve times the wavelength of the radar waves, i.e. about 2 mm to 48 mm. The inventors of the present invention have demonstrated that for a thickness of the air cavity included in the above interval, the transmission of radar waves is stronger.

[0030] The device additionally comprises a decorative coating or a surface texture which is transparent to radar waves.

[0031] A decorative coating is applied or laser-etched on the face of the body made of transparent material that is located inside the protective device.

[0032] - The body made of transparent material comprises at least two layers. Thus, a difference in thickness of the body due to the presence of the decoration can be compensated by an opposite thickness difference on another layer of the body, the two thickness differences being arranged facing each other. This allows maintaining a constant thickness of the body and thus good transparency to radar waves. In such an arrangement, the decoration can be located at the interface between the two layers, or on the face of the body that is inside the protective device. The electrically conductive heating track can be arranged at the interface between the two layers of the body made of transparent material, or on the face of the body that is inside the protective device, or on the face of the body that is outside the protective device.

[0033] - The light reflector is a removable insert. Thus, it can be added according to the lighting needs of the radome. Moreover, the use of inserts can meet the diversity of icons. The insert can thus be sized according to the size of the icon, the area to be illuminated, and / or the size of the radar cone.

[0034] - The light reflector is covered on the face situated inside the protective device with a metal, such as indium, gold or tin or any other metal that can give a "chrome appearance" and whose small thickness allows transparency to radar waves, preferably deposited by a vapor deposition ("Physical Vapour Deposition", PVD) technique. Using this technique and these metals it is possible to give the radome a metallized appearance, although metallic elements generally interfere with the transmission of radar waves.

[0035] -The light source is located outside the radar's emission cone. As a result, the light source does not interfere with the radar's operation.

[0036] The heating track comprises a connection portion which is located outside the emission cone of the radar, so that the connection portion does not interfere with the operation of the radar.

[0037] - The body made of transparent material comprises an area that is opaque to light. The light source and the connection part can thereby be hidden behind the opaque area of ​​the body made of transparent material. Alternatively, if the body made of transparent material is a vehicle grille, the connection part can advantageously be hidden in its technical area.

[0038] The heating track comprises a serpentine portion extending on the interface surface between the body made of transparent material and the emission cone of the radar. This allows uniform and complete defrosting of the portion of the radar located in the emission cone.

[0039] - The serpentine part of the heating track is a good conductor of heat. The metal properties, wire diameter and circuit length can be selected according to the area to be defrosted, the thickness of the plastic to be heated. The wire used can be based on copper, silver, tungsten or any alloy including them. For example, for CuAg alloy or pure Cu, the line resistance of the wire can be 0.15 to 15Ω.m -1 . Thermal conductivity of pure copper: 350-380W.m -1 .K -1 For pure silver wire, the thermal conductivity is 406 to 430 W.m -1 .K -1 . Properties are proprietary to the alloy selected.

[0040] - The heated portion of the heating track is transparent to radar waves. The heated portion itself is not transparent to radar waves. What makes it "invisible" to the passage of radar waves is the thickness of the heated portion, its passing frequency and the linearity.

[0041] - The heating track is visible but the small thickness does not change the light rendering.

[0042] The serpentine portion of the heating track comprises a metal wire having a diameter of less than 300 μm, preferably less than 100 μm.

[0043] - The metal wires are deposited by ultrasound on a film that is chemically compatible with the host material made of transparent material.

[0044] -The metal wires are applied by 3D deposition on a body made of transparent material.

[0045] - The heating part of the heating track can be made of conductive ink, which is deposited as a straight line with a small width and a frequency related to the frequency of radar operation. This ink-based heating system therefore does not have a serpentine design like metal wires, because each track is connected to the busbar on both sides.

[0046] The heating part of the heating track consists of a metal nanocore (nanomèche in French), preferably made of copper, silver or any other metal that allows good thermal conductivity and transparency to waves. The nanocore is connected to the busbars on both sides, so it does not have a serpentine design like conductive inks.

[0047] -The heating part of the heating channel consists of carbon nanotubes. The nanotubes are connected to the busbars on both sides, so there is no serpentine design like conductive ink.

[0048] - The reflector is assembled by any suitable means, for example by gluing, laser welding or form riveting, on the body made of transparent material and is located between the body and the radar. Preferably, the assembly is sealed against light and humidity.

[0049] -The light source is fixed on the reflector.

[0050] The light source is a conventional light source selected by a person skilled in the art from those suitable for lighting exterior parts of motor vehicles.

[0051] - The light source comprises a light emitting diode.

[0052] -The light source is located at the focus of the parabola formed by the reflective wall of the reflector. Thus, a uniform mirror effect is obtained.

[0053] The invention also relates to a combination of a radar and a radar protection device having the device features described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The invention will be better understood from the following description given by way of example only and made with reference to the accompanying drawings, in which:

[0055] Figure 1 is a schematic diagram of the positional relationship of the radar protection device relative to the radar in the prior art;

[0056] Figure 2 is a top view of a radar protection device according to one embodiment of the present invention;

[0057] Figure 3 is a schematic perspective view showing a heating track on a radar protection device according to one embodiment of the present invention. DETAILED DESCRIPTION

[0058] like Figure 1 As shown, a protective device 1 according to the prior art, i.e. a radome, is intended to be arranged in front of a radar 2. The radome 1 comprises at least one transmission area 3 through which waves 4 of the radar 2 can pass. The transmission area 3 is formed of a material that is transparent to the radar waves. The radome 1 can be fixed on a bumper of a motor vehicle, in front of the radar.

[0059] Figure 2 A radome 1 according to one embodiment of the invention is shown. The protective device 1 for a motor vehicle radar 2 comprises a body 200 formed of a material transparent to both radar waves 4 and light, two light sources 300, and a light reflector 400 formed of a material transparent to radar waves 4. These elements are arranged so that a light beam 500 emitted by the light source 300 is reflected by the light reflector 400 toward the body 200 made of a transparent material. The body 200 made of a transparent material comprises two layers 210, 220. The device 1 further comprises an electrically conductive heating track 12, which is located at the surface of the body 200 made of a transparent material. More specifically, the heating track is arranged on the face of the body located outside the protective device, which face is the face of the outer layer 210 of the body 200. The heating track can also be arranged inside the body 200 made of a transparent material, i.e. at the interface between the layers 210 and 220 of the body 200, or on the face of the body located inside the protective device (i.e. the face of the inner layer 220 of the body 200).

[0060] Reference Figure 3 , it can be seen that the heating track 12 is arranged and fixed on the face of the main body 200. The heating track 12 includes a connecting portion 18c and a heating portion 18s (here in a serpentine shape) for defrosting. The serpentine portion 18s for defrosting of the heating track 12 is arranged according to a setting compatible with the electromagnetic wave passing through the main body 200. In the example, the serpentine portion 18s for defrosting of the heating track 12 follows an ox-plowed route. The serpentine portion of the heating track is a good conductor of heat and is transparent to radar waves and light. In this example, it includes a metal wire with a diameter of less than 100 μm. The metal wire is deposited on a film by ultrasound, and the film is chemically compatible with the material of the main body made of transparent material. The film itself is deposited on the main body made of transparent material during overmolding. The metal wire can also be located on the main body made of transparent material by 3D deposition. The heating portion can also be based on conductive ink, metal (copper, silver or any other metal that allows good thermal conductivity and is transparent to waves) nanocore, or carbon nanotubes. In this case, the design is not serpentine, but a conductive heating system fed by two busbars located on both sides of the heating area. The design of these systems also allows to be transparent to the frequencies of the radar.

[0061] In this embodiment, an air cavity 20 is provided between the light reflector 400 and the transparent body 200 .

[0062] The reflector 400 is assembled on the body 200 made of transparent material by any suitable means (such as gluing, laser welding or riveting), and is located between the body 200 and the radar 2. The assembly is sealed against light. The light source 300 is fixed on the reflector 400.

[0063] The reflector 400 has a gradually widening U-shape. This shape is only schematic and not restrictive. In another embodiment (not shown), the reflector can have a curved shape, forming a parabola at which the light source 300 is located at its focus. The reflector 400 is covered with indium deposited by a vapor deposition (PVD) technique on the face located inside the protective device 1. The reflector 400 is a removable plug-in.

[0064] The light sources 300 include light emitting diodes (LEDs) and are located outside the radar's emission cone 600. As a result, they do not interfere with the operation of the radar. It is also conceivable to use light sources that are transparent to radar waves, such as organic light emitting diodes (OLEDs).

[0065] The serpentine portion 18s of the conductive heating track 12 arranged at the surface of the body 200 made of transparent material extends on the interface surface between the body 200 made of transparent material and the emission cone 600 of the radar 2. The connection portion of the conductive heating track 12 is located outside the emission cone 600 of the radar 2.

[0066] On the layer 220 of the transparent body 200, a decorative coating (not shown) is applied on the face of the body situated inside the protective device 1. The decoration can also be located at the interface between the two layers 210 and 220. It can also be etched by laser. It can also consist of a surface texture of one of the layers 210, 220.

[0067] The body 200 includes two areas (not shown) that are opaque to light, behind which the light source 300 and the connecting portion 18c of the heating track 12 are hidden.

[0068] The present invention is not limited to the embodiments described, and other embodiments will be apparent to those skilled in the art.

[0069] Reference numerals list

[0070] 1: Radome

[0071] 2: Radar

[0072] 3: Transmission area

[0073] 4: Radar waves

[0074] 12: Heating pipe (piste)

[0075] 18c: Connection part

[0076] 18s: Heating part

[0077] 20: Air cavity

[0078] 200: A body made of a material that is transparent to radar waves and light

[0079] 210: The surface of the body made of transparent material facing the outside of the protective device

[0080] 220: The surface of the body made of transparent material facing the inner side of the protective device

[0081] 300: Light source

[0082] 400: Light reflector

[0083] 500: Beam

[0084] 600: Radar emission cone

[0085] 700: Light Emitting Diode

Claims

1. A motor vehicle radar (2) protection device (1), characterized in that: The protection device (1) comprises the following elements: - a body (200) formed of a material transparent to both radar waves (4) and light; - a light source (300); - a light reflector (400) formed of a material transparent to said radar waves (4); and - an electrically conductive heating track (12) arranged inside or at the surface of a body (200) made of a transparent material, These elements are arranged so that the light beam (500) emitted by the light source (300) is reflected by the light reflector (400) toward the main body (200) made of a transparent material. An air cavity (20) is provided between the light reflector (400) and the transparent body (200).

2. The motor vehicle radar (2) protection device (1) as claimed in claim 1, further comprising a decorative coating or surface texture which is transparent to the radar waves.

3. A motor vehicle radar (2) protection device (1) according to claim 1 or 2, wherein: The body (200) made of a transparent material comprises at least two layers (210, 220).

4. A motor vehicle radar (2) protection device (1) according to claim 1 or 2, wherein: The light reflector (400) is a detachable insert.

5. A motor vehicle radar (2) protection device (1) according to claim 1 or 2, wherein: The light reflector (400) is covered on the face situated inside the protective device with indium, gold or tin or any other metal capable of presenting a "chrome look" and whose small thickness allows transparency to the waves of the radar.

6. The motor vehicle radar (2) protection device (1) according to claim 5, characterized in that The indium, gold or tin or any other metal capable of presenting a "chrome look" and whose small thickness allows transparency to the waves of the radar is deposited by physical vapor deposition techniques.

7. A motor vehicle radar (2) protection device (1) according to claim 1 or 2, wherein: The light source (300) is located outside the emission cone (600) of the radar (2).

8. A motor vehicle radar (2) protection device (1) according to claim 1 or 2, wherein: The heating track (12) comprises a connecting portion (18c) located outside the emission cone (600) of the radar (2).

9. A motor vehicle radar (2) protection device (1) according to claim 1 or 2, wherein: The body (200) made of a transparent material includes a region that is opaque to light.

10. A motor vehicle radar (2) protection device (1) according to claim 1 or 2, wherein: The heating track (12) includes a heating portion (18s) extending on an interface surface between the body (200) made of a transparent material and an emission cone (600) of the radar (2).

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